1. Technical Field
The present invention relates to compositions useful for reducing the amount of formaldehyde released, for example, from durable press treated fabrics and during the manufacture of particleboard. More particularly, the present invention relates to compositions useful as formaldehyde scavengers which are uniquely effective in reducing the amount of formaldehyde released from durable press treated fabrics and during the manufacture of particleboard, and subsequently without detracting from the properties of the fabrics or the particleboard.
The term "fabric" as used herein means products and objects made from natural textile fabrics such as jute, sisal, ramie, hemp, and cotton as well as many of the synthetic organic fibers, such as rayon, cellulose esters, vinyl resin fibers, polyacrylonitrile and copolymers thereof, polymers and copolymers of olefins such as ethylene, polyimide or nylon types, and the like. The fabrics used can be those of a single composition or a mixture of fibers.
The term "durable press treated fabric" as used herein means fabrics as described above which have been imparted with crease and wrinkle resisting properties under both wet and dry conditions by heating, drying, and curing with a finishing agent such as glyoxal resin, formalin, ureaformaldehyde resin, dimethylolurea, dimethyl ether of ureaformaldehyde, melamine formaldehyde resins, cyclic ethylene urea formaldehyde resins, e.g. dimethylol urea, triazine-formaldehyde resins, triazone formaldehyde resins and the like which are well known in the art and need not be described in detail here.
The term "particleboard" as used herein means an article used in construction of buildings. It is manufactured by compressing sawdust mixed with a resin and heating to cure the resin. The resin is normally a formaldehyde resin.
2. Description of Background Art
The uses of formaldehyde and formaldehyde-derived products have been fundamental in the modernization of chemical finishes in the textile industry and for the dry process manufacturing technique in the particleboard industry. Associated with the use of these products, however, is the formation of free or releasable formaldehyde in finished fabrics or garments and during the heating cycle of the manufacture of particleboard, especially if the finished board is exposed to heat and/or humidity.
The released formaldehyde is severely irritating to the eyes, mucous membranes and skin. It is toxic if ingested and has been reported as a suspect human carcinogen with prolonged exposure of vapor at high concentrations. Accordingly, there has been increasing pressure by environmental consumer and labor groups to minimize the amount of formaldehyde released for example, from chemically treated fabrics or particleboards. The federal Occupational Safety and Health Administration ("OSHA") currently is considering proposals that call for limits as low as 0.1 to 0.5 ppm of formaldehyde in the atmosphere at the workplace. Current acceptable formaldehyde emission levels for particleboard are found in the Federal Register, 24 C.F.R., Part 3280, using the Large Chamber Test Method FTM-2 with an upper limit of 0.3 ppm.
Chemical finishing procedures using formaldehyde and formaldehyde derived products are performed principally on those fabrics which are composed either entirely or in part of cellulosic fibers, i.e., cotton and rayon. These fibers have chemically reactive sites (hydroxyl groups) which lend themselves to chemical modification and treatments. Of particular importance in this regard is the treatment of rayon and cotton containing fabrics with difunctional reagents which are capable of chemically cross-linking the cellulose chains comprising the fibers. Such reactions improve fiber resilience, thereby enhancing wrinkle resistance and recovery, as well as imparting durable press characteristics to the treated fabrics.
Modern durable press finishing processes follow very closely the original
(Tootal, Broadhurst, Lee) process based on water-soluble methylolurea. The fabrics to be treated are padded, foam finished or otherwise impregnated in a continuous manner with a solution of finishing chemicals containing a formaldehyde-derived cross linking agent and a curing catalyst. The finishing composition ordinarily contains additional compositions such as weight builders and hand modifiers. e.g., softening agents and stiffening agents. Following impregnation, the fabrics are frame dried to fixed dimensions and cured at elevated temperatures. Fabrics finished in this manner are said to possess a memory. For example, a fabric cross-linked in the flat, dry state will return to that state after washing when it is given an opportunity to shed its wrinkles in a tumble dryer.
A urea-glyoxal formaldehyde adduct, 1,3-dimethyl-ol-4,5-dihydroxyethyleneurea (DMDHEU), has been the primary cross-linking agent in use in the United States since enthusiastic customer acceptance of permanent press products in 1965 prompted a shift from the use of the cyclic ureas, i.e. alkyleneureas, urons and triazones, to a cross-linking system which is lower in formaldehyde release and more resistant to hydrolysis. DMDHEU, a N-methylol cross-linking agent, represents at present the optimum cross-linking agent for fabrics which are composed either entirely or in part of cellulose fibers. The cross-linking reaction of DMDHEU with cellulose is believed to occur principally through the reaction of the pendant DMDHEU N-methylol groups with the hydroxyl groups of the cellulose.
Prior to 1965, it was not unusual for unwashed finished products to release 3,000-5,000 ppm formaldehyde when tested by the AATCC Test Method 112-1978 (Sealed Jar Method). The Sealed Jar Method measures formaldehyde release as a vapor from a fabric stored over water in a sealed jar for 20 hours at 49.degree. C. or 4 hours at 65.degree. C. A reduction in the release of formaldehyde to 2,000 ppm and later 1,000 ppm, was achieved largely through the introduction of DMDHEU as the primary cross-linking agent in durable press finishing processes.
The amount of formaldehyde released as a vapor from a fabric under ambient air conditions (temperature: 23.degree. C..+-.1.degree., relative humidity 55%.+-.2%) can also be measured by the dynamics chamber test method. (Roberts, Eugene C. and Rossano, Anthony J. Jr., AATCC; Vol. 16, No. 3, p. 29 (1984).
The modification or alkylation of DMDHEU through the addition of one or more polyhydric alcohols, such as diethylene glycol and sorbitol, to the finishing composition is known to further reduce the amount of formaldehyde released by durable press treated fabrics. Capping of pendant DMDHEU N-methylol groups by the polyhydric alcohols prevents the formation of free formaldehyde in the finishing composition and may reduce formaldehyde release by as much as 50%. Nevertheless, the amount of formaldehyde released from fabrics treated with modified or alkylated DMDHEU remains higher than is acceptable to environmental, consumer and labor groups. Furthermore, in the chemical treatment of fabrics, DMDHEU is generally not the sole source of free formaldehyde. Ordinarily, dyeing and finishing chemical requirements are such that supplemental formaldehyde or formaldehyde-derived chemicals such as dye fixatives, hand modifiers, etc., account for a formaldehyde release which can be substantially higher than that obtained from a simple durable press finishing composition consisting solely of a cross-linking agent and a catalyst.
The incorporation of a formaldehyde scavenger for example, into durable press finishing compositions and the urea formaldehyde resin is known to reduce the amount of formaldehyde released from durable press treated fabrics and from particleboard respectively. The formaldehyde scavengers reportedly react by two mechanisms. In one mechanism the formaldehyde scavenger may react with free formaldehyde in the finishing composition or the urea-formaldehyde resin to form a stable addition compound at the curing temperature. Alternatively, the formaldehyde scavenger may prevent the formation of free formaldehyde in the finishing composition by capping pendant DMDHEU N-methylol groups and free N- methylol groups produced by the hydrolysis of the cross link.
An effective formaldehyde scavenger useful in the finishing composition must be water-soluble and able to penetrate the fiber at the reaction site. In addition, an effective formaldehyde must be nonvolatile under curing conditions and compatible with the chemicals of the finishing composition or the urea-formaldehyde resin composition. It must not be so basic as to inactivate the catalyst and promote hydrolysis of the N methylol groups to N-H and formaldehyde. At the same time, it must not be so acidic as to hydrolyze the cross link during the sealed jar test. A formaldehyde scavenger must not adversely affect fabric properties such as hand, shrinkage, mullins burst and shade or whiteness or the mechanical properties of the particleboard. And, of course, it must be economical to use in production and efficient at reasonable levels such as 1-3% solids on the weight of the bath ("owb").
Heretofore, the prior art has not disclosed a formaldehyde scavenger, suitable for use in the durable press treatment of fabrics or in the maintenance of particleboard, which is effective in reducing released formaldehyde to the low levels which are currently desired without detrimental effects on fabrics or particleboard properties. Currently, the formaldehyde scavengers most widely used in durable press finishing compositions are polyhydric alcohols, such as diethylene glycol and sorbitol and in the manufacture of particleboard are nitrogen containing compounds such as urea, melamine, diazine, triazine and amine compounds (U.S. Pat. No. 4,559,097). Compounds such as these, however, are not sufficiently effective in reducing formaldehyde levels to produce the low levels which are currently desired.
Nitrogenous compounds such as urea, ethyleneurea and, in particular, carbohydrazide are known to effectively reduce formaldehyde levels but only at the expense of the properties of the fabrics. Residual amide (--CONH) groups in the treated fabrics cause chlorine retention and possible fabric yellowing as well as a reduction in the lightfastness of certain azo dyes. These side effects preclude the wide use of nitrogenous compounds as formaldehyde scavengers in durable press finishing processes. Further the nitrogenous compounds and the resin components of the urea-formaldehyde resin composition may react, decreasing the strength of the particleboard. These side effects preclude the wide use of nitrogenous compounds as formaldehyde scavengers in particle board.
Dimethyl-1,3-acetonedicarboxylate, diethyl malonate and ethylacetoacetate, three active methylene compounds, have been suggested by Tomasino et al, in Textile Chemist and Colorist, Vol. 16, No. 12, Dec. 1985, as possible formaldehyde scavengers, with dimethyl-1,3-acetonedicarboxylate being particularly effective in reducing formaldehyde release under laboratory conditions. In laboratory tests, these compounds are found to be effective in reducing the amount of formaldehyde released by fabrics treated with a durable press finishing composition comprising DMDHEU, without detrimental effects on fabric, properties. These compounds, however, are insoluble in water or of low solubility and therefore are not suitable for use in present durable press finishing processes.